Compression seals for sealing expansion joints, or movement tolerance spaces, between adjacent dynamic members such as concrete slabs in bridges, parking decks and the like are well-known. Typically, such a compression seal is formed as an elastomeric extrusion of indeterminate length and having a cross-sectional configuration designed to collapse in a controlled manner to accommodate thermal expansion and contraction of the adjacent structural members. When the seal is installed in the movement tolerance space between adjacent concrete slabs, the seal is compressed as the slabs thermally expand; and as the slabs thermally contract, the resilient seal expands to maintain constant contact with the opposing vertical walls of the adjacent structural members, thereby providing a weatherproof seal of the expansion joint.
There are a number of problems associated with such prior art compression seals. When used for pedestrian traffic applications, the compression seal must expand and collapse while maintaining a substantially planar upper surface. If the upper surface of the seal bows upwardly as the seal is compressed, the seal will protrude above the adjacent structural members such that pedestrians can trip over it, or such that it can become dislodged by snow plows and the like. Conversely, if the upper surface of the seal collapses downwardly as the seal is compressed, women's high heels can easily become lodged in the depression. Further, dirt and debris can accumulate in such depressions, accelerating wear on the seal or impairing movement of the joint.
In addition, in many applications the seal must not only maintain a watertight seal but must also be capable of supporting a vertical load, which typically requires more or thicker seal walls, increasing the cost of the seal. If a direct loading of the seal exceeds the seal's resistance to vertical forces, the seal can become dislodged from the joint walls, causing a loss of watertight integrity. Finally, use of the seal in sunlit areas exposes the seal to ultraviolet radiation, which accelerates aging of the elastomer. Since the seal is dependent upon its elasticity in order to maintain an effective seal between the adjacent structural members, such accelerated aging of the elastomer can result in premature seal failure.
An alternative approach to covering the movement tolerance space between adjacent dynamic members is the surface cover plate. The cover plate is coplanar with the upper surfaces of the adjacent members and is fixed to one of the adjacent members and movable with respect to the other. As the members expand and contract, the free end of the cover plate slides relative to the adjacent slab. The flat upper surface of the cover plate is well-suited to pedestrian traffic. The cover plate is better suited to accommodating vertical forces than a compression seal, since the plate bears downwardly against the horizontal upper surfaces of the adjacent members, rather than being dependent upon frictional contact with vertical surfaces to support a vertical load. And, the cover plate provides a more aesthetically pleasing appearance than a compression seal. However, the cover plate is neither watertight nor airtight and is thus poorly suited to applications where providing a barrier against the elements is necessary.
Accordingly, there is a need to provide an apparatus for sealing the movement tolerance joint between adjacent structural members which is conducive to pedestrian traffic, and yet provides an airtight and watertight seal.
Efforts have been made to combine a compression seal and a cover plate into an integrated unit. One such example is found in French Pat. No. 2,250,003, which discloses a compression seal of circular cross-section and a joint cover connected to the upper central portion of the circular compression seal by a stem. When the compression seal is installed within the movement tolerance space between adjacent structures, one edge of the joint cover is glued to an adjacent structure, the other edge of the joint cover moving with respect to the opposite structure as the joint opens and closes. However, this device suffers from the disadvantage that the circular seal distorts upwardly as the joint is compressed, which upward distortion tends to displace the connecting stem upwardly, forcing the joint cover upwardly. Over time, and with exposure to moisture and temperature extremes, the adhesive bond between the joint cover and the adjacent structure may weaken, permitting the joint cover to be lifted off the joint as the seal is compressed, with the result that the integrity of the joint is compromised.
One effort to overcome this problem is shown in British Pat. No. 956,706, which discloses another design of a compression seal with attached joint cover. The compression seal has a generally V-shaped sectional configuration, and the joint cover is attached to the seal at the vertex of the "V". In this manner, as the joint closes, compressing and distorting the seal, the vertex is displaced downwardly. The stem is thereby placed under tension, pulling the joint cover firmly downward against the upper surface of the adjacent structures. While this design appears to solve the problem of the joint cover lifting away from the adjacent structures as the seal is compressed, a new problem is presented. As the joint opens and the seal expands, the vertex of the "V" is now displaced upwardly, thereby applying an upward force to the stem, again lifting the joint cover away from the surface of the adjacent structures. Thus, rather than the joint cover being displaced as the seal is compressed, the joint cover is now displaced as the seal expands.
Thus, there is a need to provide a combination compression seal and cover plate wherein the cover plate is not dependent upon an adhesive bond to maintain firm contact with the upper surfaces of the adjacent structures.
There is a further need to provide a combination compression seal and cover plate wherein the cover plate is not displaced upwardly off the upper surfaces of the adjacent structures as the joint opens or closes.